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以砷含量为7.63%的砷钙渣为研究对象,利用磷渣基地聚物材料对其进行固化处理,并采用毒性浸出实验考察了砷钙渣及固化体砷毒性浸出特性。结果表明:砷钙渣中砷的毒性浸出浓度可达2 450 mg/L,远超过国家毒性浸出鉴别标准限值(5 mg/L)。考察了不同养护时间、不同p H值(1~12)浸取剂环境下固化体中砷的浸出规律。结果表明:在p H=4~8范围内,砷浸出浓度较小;在酸性(p H<4)和碱性(p H>8)条件下砷浸出相对较大,但均小于5 mg/L。并考察了固化体中砷形态变化规律,揭示其固化机理。当养护时间为28 d时,固化体中As(Ⅲ)含量由96.3%降至28.8%,其后随着养护时间的变化固化体中As(Ⅲ)含量呈缓慢降低趋势,180 d As(Ⅲ)含量为12.6%,240 d As(Ⅲ)含量为10.8%。磷渣基地聚物固化砷钙渣机理为:磷渣基地聚物材料水化环境和所含的铁氧化物可使高毒性及强迁移性As(Ⅲ)向相对稳定的As(Ⅴ)转化;随时间的变化,磷渣基地聚物材料不断水化,并提供游离Ca2+、Al3+离子,使砷化合物经沉淀反应生成Al-As-O、Ca-As-O难溶性盐,进而降低砷浸出浓度。
The arsenic and calcium slag with arsenic content of 7.63% was used as the research object, the phosphorus slag base material was used to solidify it, and the toxicity leaching experiment was used to study the arsenic residue and arsenic toxicity leaching characteristics. The results showed that the concentration of arsenic in arsenic calcium residue was up to 2 450 mg / L, far exceeding the national standard of 5 mg / L for identification of toxic leaching. The leaching behavior of arsenic in cured body under different curing time and different p H value (1 ~ 12) was studied. The results showed that the arsenic leaching concentration was small in the range of pH 4 ~ 8, and the arsenic leaching was relatively large under the conditions of acidity (p H <4) and alkaline pH (p H> 8) L. The changes of arsenic species in the solidified body were also investigated, and the curing mechanism was revealed. When the curing time was 28 d, the content of As (Ⅲ) in the cured body decreased from 96.3% to 28.8%, then the content of As (Ⅲ) in the cured body decreased slowly with the curing time, and the content of As ) Content of 12.6%, 240 d As (Ⅲ) content of 10.8%. The mechanism of arsenic and calcium slag solidified by phosphorus slag base polymer is as follows: the hydrous environment of phosphorus slag base polymer material and the iron oxide contained therein can convert As (Ⅲ) to As (Ⅴ) with relatively high toxicity and strong mobility; Over time, the phosphorus slag base polymer materials continue to hydrate, and provide free Ca2 +, Al3 + ions, the arsenic compound precipitation reaction of Al-As-O, Ca-As-O insoluble salts, thereby reducing the concentration of arsenic leaching .